System Development and Technology Aspects of the IBM 3081 Processor Complex

The IBM 3081 Processor Complex consists of a 3081 Processor Unit and supporting units for processor control, power, and cooling. The Processor Unit, completely implemented in LSI technology, has a dyadic organization of two central processors, each with a 26-ns machine cycle time, and executes System/370 instructions at approximately twice the rate of the IBM 3033. This paper presents an overview of the advances in technology and in the design process, as well as enhancements in the system design that were associated with the development of the IBM 3081. Application of LSI technology to the design of the 3081 Processor Unit, which contains almost 800,000 logic circuits, required extensions to silicon device packaging, interconnection, and cooling technologies. A key achievement in the 3081 is the incorporation of the thermal conduction module (TCM), which contains as many as 45,000 logic circuits, provides a cooling capacity of up to 300 W, and allows the elimination of one complete level of packaging—the card level. Reliability and serviceability objectives required new approaches to error detection and fault isolation. Innovations in system packaging and organization, and extensive design verification by software and hardware models, led to the realization of the increased performance characteristics of the system.